Communication - Algodue ELETTRONICA 485-MDB-20 Instrucciones De Servicio

COMMUNICATION

The JBUS/MODBUS used by the 485-MDB-20 in-
®
volves a dialogue using a master-slave hierarchical
structure. There are two possible dialogues:
• the master communicates with a slave (UPA) and
waits for its reply
• the master communicates with all the slaves (UPA)
without waiting for their reply.
THE STANDARD COMMUNICATIONS FRAME
The standard communications frame consists of:
Slave address
According to the JBUS/MODBUS
sion time must be less than 3 silences, i.e. the emission
time of 3 characters so that the message is processed
by the UPA20.
To correctly use information, the following functions
are important:
3 : to read n words (maximum 128).
6 : to write one word.
8 : to diagnose exchanges between the master and
the slave via meters 1, 3, 4, 5 and 6.
16 : to write n words (maximum 128).
Function code
protocol, transmis-
®
The mode of communication is the RTU (Remote Ter-
minal Unit) using hexadecimal characters of at least 8
bits.
Address Data
NB:
When selecting slave address 0, a message is sent to
all the instruments present on the network (only for
functions 6 and 16).
For further details on protocol, refer to MODBUS
protocol for UPA20.
485-MDB-20 - JBUS/MODBUS
COMMUNICATION
CRC 16
485-MDB-20
®
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